Conjugated polymers and conducting polymers based on them were discovered in the late 1970s. They offer unique optical (color) properties and the possibility of combining the important electronic and optical properties of semiconductors and metals with the attractive mechanical properties and processing advantages of polymers. However, the initial conjugated polymer systems were insoluble, intractable, and nonmelting (and thus not readily processable into oriented structure) with relatively poor mechanical properties.
In recent years, progress has been made toward specific conjugated polymer systems which are more soluble and thereby more processable. For example, the poly(3-alkylthiophene) derivatives (P3ATs) of polythiophene are soluble and meltable with alkyl chains of sufficient length, and the P3ATs have been processed into films and fibers See, e.g., Hotta, S., et. al., Macromolecules, 20:212 (1987); Nowak, M., et. al., Macromolecules, 22:2917 (1989); Hotta, et. al., Synth. Met., 26:267 (1988). However, because of the moderate molecular weights and/or the molecular structures of these polymers, the mechanical properties (modulus and tensile strength) of fibers and films, etc., of the P3ATs are modest and limit their use.
Alternative methods of processing conjugated polymers have been developed. For example, conjugated systems based on poly(phenylenevinylene) ("PPV") and alkoxy derivatives of PPV have been synthesized via the "precursor polymer" route. See, for example, U.S. Pat. Nos. 3,401,152 and 3,706,677 to Wessling et. al.; Gagnon et. al., Am. Chem. Soc. Polym. Prepr. 25:284 (I984); Momii et. al., Chem. Lett. 1201-4 (1988); and Yamada et. al., JCS Chem. Commun. 19:1448-9 (1987). In the first step of this route, a saturated precursor polymer is synthesized. The precursor polymer is soluble and can be processed into the desired final shape. The precursor polymer is thermally converted into the conjugated polymer during or after the forming into desired final shape. Tensile drawing can be carried out during the thermal conversion. Thus, significant chain extension and chain alignment of the resulting conjugated polymers can be achieved. Although the precursor polymer route may offer advantages, the multi-step synthesis is complex, makes the resultant materials relatively expensive, and limits their utility.
Commonly owned U.S. patent application Ser. No. 468,737, filed on Jan. 24, 1990, disclosed that shaped articles can be formed of composites of conjugated polymer and flexible-chain carrier polymers This earlier application is incorporated by reference. The process and articles of that invention seek to marry the desirable properties of conjugated polymers with the desirable properties of non conjugated polymers such as ultra-high molecular-weight poly(ethylene) "UHMW-PE".
UHMW-PE can be chain-extended and chain-aligned by first dissolving the polymer in an appropriate solvent at an elevated temperature, then forming a gel by cooling, and subsequently carrying out tensile drawing at selected conditions (temperature, time, etc.) to yield fibers and films etc. with outstanding mechanical properties.
U.S. Ser. No. 468,737 discloses that these properties are retained and that the conductive and optical properties of conjugated polymers can be gained by its composite systems.
We have now made further improvements to these non-conjugate/conjugate polymer composite systems and their preparation and processing.